there's tons of information to be had by searching through the forums and reading the faqs. a lot of the questions you're asking have no definite answer, mostly opinion based.
Companies pay out a lot of money to convince you that their product is the "best". whats best for you might not be best for someone else. hypothetically, is best for you to spend top dollar on a huge lift and beefy tires, and then not being able to afford gas and payments?
sidewall is measured in ply. every tire has advertised ply amounts
tread life varies by cut and brand(a/t, mud, etc)
the best thing you can do is read and research and when you come to something that doesn't make sense, ask away. but at least put in the effort first. a lot of your questions would be answered by going to the manufacturer's site and looking at that specific product. Its all right there, so you might as well go look for yourself.